The present invention relates to an electric/acoustic transducer module for behind-the-ear or in-ear hearing aids as defined in the preamble of claim 1, further an in-ear hearing aid as defined in the preamble of claim 10 and a manufacturing method for such an in-ear hearing aid as defined in the preamble of claim 21.
As regards hearing aids and in particular in-ear hearing aids, care must be taken to preclude the loudspeaker housing from being connected by a mechanically rigid bridge to the auditory canal in order that acoustic feedback from the loudspeaker to the receiving microphone shall be eliminated as far as possible. Furthermore the space available to hearing aids in general will be exceedingly limited and must be used optimally.
Illustratively the European patent document 0 548 580 discloses fitting the electric/acoustic transducer system of an in-ear hearing aid with a loudspeaker housing, the motor-driven loudspeaker diaphragm and the motor drive being appropriately supported. Said diaphragm or the motor drive are so supported relative to said loudspeaker housing that the diaphragm-driven acoustic signals are directly transmitted to said loudspeaker housing. The said assembly is so configured in an in-ear hearing-aid housing that this loudspeaker housing shall be as far away as possible from said hearing-aid housing, whereby only reduced acoustic transmission bridges are formed. As a result, however, assembly of the heretofore known hearing aids demands meticulous care that such bridges shall not form, that is, a transducer system must be inserted manually, as is actually the case in practice, into the hearing-aid housing and therein it must be aligned most carefully.
The objective of the present invention is elimination of the above drawbacks. To that end the electric/acoustic transducer module is characterized by the features of claim 1.
Because the loudspeaker housing is resiliently supported in the enclosure, the transducer module can be integrated in geometrically locking and even in frictionally locking manner into a behind-the-ear or in-ear hearing aid. Furthermore the gap already cited and anyway required between the housings of the loudspeaker and of the hearing aid now shall be exploited to acoustically improve the hearing-aid behavior. This goal is attained in that the gap which the invention places at the transducer itself shall raise the bass range of the transducer module by several dB because the said gap acoustically enlarges by a multiple the chamber at the rear of the diaphragm when compared with this rear chamber in the loudspeaker housing per se. Reference is made in this respect to U.S. Pat. No. 3,257,516 which discusses the advantages of large rear chambers.
In one preferred embodiment, the enclosure acts as a magnetic shield and for this purpose is preferably made of mu-metal. Very simple assembly and disassembly of the transducer system, in particular the insertion of the loudspeaker housing together with the loudspeaker, is attained in that the enclosure comprises a cup-shaped component which preferably is metallic. In a further preferred embodiment, and following insertion of loudspeaker housing with loudspeaker, this cup-shaped element is sealed by a cover comprising the transducer system""s acoustic output which comprises the transducer system""s acoustic output. In a far more preferred embodiment, said cover element comprises an aperture where, by means of a membrane, the first chamber on one side of the loudspeaker diaphragm, that is that chamber which is coupled to the acoustic output of the transducer system, is separated from the ambience. Said membrane is situated in unhampered manner across the aperture. In another embodiment, the cup is complemented by hose-like elastomeric cover. Both designs practically achieve sealing the inside of the transducer module, this feature being highly desirable in particular as regards the known soiling of acoustically significant transmission elements of in-ear hearing aids. Said designs at once allow removing such soiling from the transducer module. Neither dirt nor moisture can enter the module.
The membrane of the above preferred embodiment differs from the corresponding design in the aforementioned European patent document 0 548 580 by being mounted in freely vibrating manner and not being motor-driven. By expertly dimensioning the acoustically effective chambers of the invention and expertly determining the membrane characteristics in the sense of impedance matching, the invention achieves virtually precluding said membrane from affecting the hearing-aid""s transmission characteristics at the transmission side of the loudspeaker.
In an especially preferred embodiment of the invention, at least the unobstructed portion of the membrane shall be homogeneous in its material and in a further preferred feature shall be of constant thickness. This design offers minimal effort in driving the cited membrane and allows overviewing the acoustic behavior of this membrane.
In a preferred embodiment, at least the free portion of the cited membrane shall be made of an elastomeric material such as latex or silicone rubber, further it shall be most economical and uniform and thin, tough and unobjectionable as regards being in contact with living tissue. Preferably the membrane shall be airtight. Its thickness preferably is dxe2x89xa60.09 mm.
Furthermore, to allow installing the loudspeaker housing in a most simple manner in the enclosure while preserving the decoupling of loudspeaker housing and enclosure, the invention proposes supporting the loudspeaker housing by means of elastic supports in said enclosure. Also, to optimally exploit said gap, a further embodiment proposes that the said gap shall omnidirectionally enclose the loudspeaker housing except for this loudspeaker housing""s support sites on the said enclosure.
The in-ear hearing of the invention comprises an electric/acoustic transducer system of the above discussed kind. The potential for simple assembly is exploited to the fullest in that the transducer module""s enclosure is configured in geometrically and/or frictionally locking manner in the hearing-aid housing.
As a result and as shall be elucidated further below, such hearing aids may be manufactured in automated manner: the problem of avoiding acoustic bridges between the housings of the loudspeaker and of the hearing-aid is solved a priori by installing the transducer module of the invention.
In this respect and in a preferred embodiment of the invention, the transducer module""s acoustic output can be conventionally connected by a tubular stub to the acoustic output of the hearing-aid housing.
In another preferred embodiment of in-ear hearing aid of the invention, a membrane is always used which is mounted so as to be vibrating in unhampered and undegraded manner and which separates the hearing-aid ambience from the first chamber at the transducer module of the invention. This membrane obviously can consist of the previously cited membrane itself at the transducer system, though this feature is not mandatory, and in all cases the pertinent embodiment modes shall apply. On the other hand, in a further preferred embodiment, the said membrane is directly mounted in the vicinity of the acoustic output of the hearing aid. In this way soiling penetrations are reliably precluded not only into the transducer module but also into the hearing aid""s transducer input.
Therefore, in a further preferred embodiment of the hearing aid of the invention, the acoustic output of the transducer module of the invention is essentially situated directly at the output aperture of the hearing-aid housing, whereby said membrane, if preferably provided, is directly situated in the environment of the hearing-aid housing on one hand and directly at the transducer module""s output on the other hand. Accordingly, and as already mentioned, on one hand the problem of dirt collecting at an output aperture of the hearing aid is being solved in that said aperture is directly sealed by said membrane, and on the other hand the feasibility is provided to optimize the acoustic behavior in the sense that no additional, intermediary transmission paths are needed between the transducer module""s output and the acoustic hearing-aid output. The remaining acoustic transmission path can be designed solely considering impedance matching.
In an especially preferred design of the hearing aid, the acoustic output of the hearing-aid housing consists of a lamellar element connected for instance by welding or bonding to the remaining hearing-aid housing. Preferably this design also shall include sealing said output aperture using a membrane which now however shall be preferably integral with said element. The above cited considerations also apply to this membrane, and as a consequence said element preferably shall consist of an elastomeric material such as latex or silicone rubber.
The method of the invention for manufacturing a hearing aid, in particular an in-ear hearing aid of the invention, is characterized in that the transducer module is configured in geometrically or frictionally locking manner inside the hearing-aid housing. As a result, the transducer module can be accurately positioned at little effort in the hearing-aid housing, or it may even be force-fitted between portions of the hearing-aid housing, or illustratively this transducer module may be cast jointly with the hearing-aid housing.
As a result, the preferred implementation of the above method shall be made possible, that is, to insert in automated manner the transducer module into the hearing-aid housing.
In another preferred implementation, the transducer module is inserted through an aperture constituting the acoustic output of the hearing-aid housing, that is, from below, into said housing. This feature allows a further procedure, namely positioning the transducer module into a seating aperture of a support plate and, by means of a relative motion between the support plate and the hearing-aid housing, inserting the transducer module from the acoustic output of the hearing-aid housing into this housing. The automation so made feasible is quite clear to the expert: a plurality of receiving apertures in said support plate shall receive the corresponding number of transducer modules which are inserted from below into a corresponding number of housings of in-ear hearing aids to be manufactured.
In a further preferred implementation of the invention, the support plate subsequently is used as a portion of the hearing-aid housing by being connected to it, preferably by bonding or welding and thereupon being trimmed off along the outside contour of the hearing-aid housing.
In another preferred implementation of the method of the invention, the receiving aperture for the transducer module to be seated in the support plate takes the form of a blind aperture, as a result of which and in a further preferred implementation, the base of the blind aperture shall constitute the above-mentioned membrane which is integral with the support plate or mounted on it as a sheet-like structure. If the cover of the blind aperture shall be the membrane as discussed above, and being integral with the support plate, then, clearly this support plate is also made of a material meeting the requirements of a membrane material, that is, it shall preferably be elastomeric, for instance a latex or silicone rubber.